At my dojo, we hold an eight week "learn about Aikido" class through the college. At the first class, bowing is explained as a sign of respect and not a religious thing. Of course you leave room to interpret the spiritual parts as the individual will.

The city in which I live harbors one metric ton of religions from atheist (yup, that's a religion too) to the far extreme. Explaining Aikido in generic terms off the bat is usually a good way of keeping people from running for the hills thinking that they are joining a cult.

Although one guy (who didn't stay very long) had a real problem with bowing to anybody. Said it was against his religion. I don't know what religion that was though.

I don't find it to be religious. We have Buddhists who are senior students but never have I seen them integrate their beliefs into the class curriculum. Just the same with other religions as well at the dojo. I suppose like many things, you can take it and make it your own or adapt it to your beliefs at will without corrupting the core of what Aikido is.